KR100905715B1 - Hard disk drive apparatus and method to determine contact between a head and a disk of a hard disk drive - Google Patents

Abstract

Disclosed are a method for determining a contact point between a FOD head and a disk and a hard disk drive including a fly on demand (FOD) head. The head includes a heating coil capable of receiving various levels of power. The determination method includes determining head position estimation error data. Deviation values in the estimation error data are generated by different power supply values and used to determine the point of contact between the head and the disk. The determination method also collects a plurality of amplification gain control signals (SAGC) and calculates an average of the SAGC values. The average of the SAGC values at different power levels is generated and used to determine the point of contact between the head and the disk.

Description

Hard disk drive apparatus and method to determine contact between a head and a disk of a hard disk drive}

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

1 shows monitoring in the prior art used to determine the head contact point and is a graph showing the position error signal PES value according to the voltage V. FIG.

2 is a front view of a hard disk drive device according to the present invention.

3 is an enlarged view of a head of the hard disk drive of FIG. 2.

4 is a schematic diagram illustrating an electrical circuit in the hard disk drive of FIG. 2.

FIG. 5 is a diagram schematically illustrating a read channel in the electrical circuit of FIG. 4.

FIG. 6 is a diagram schematically illustrating a servo loop of the hard disk drive of FIG. 2.

7 is a flowchart illustrating a process in accordance with the present invention for performing calculations to collect data and obtain data that can be used to determine contact between the head and the disk.

8 is a graph showing the deviation value of the power level supplied to the heating coil of the head versus the head position measurement error.

9 is a graph showing the power level supplied to the heating coil of the head versus the average SAGC value.

** Description of the symbols for the main parts of the drawings **

10: hard disk drive (HDD- hard disk drive)

12: disk

14: spindle motor

16: base plate

18: cover

20: head

22: writing element

24: reading element

26: flexure arm

28: actuator arm

30: bearing assembly

32: voice coil

36: voice coil motor

38: printed circuit board assembly (PCB assembly)

40: integrated circuit

42: printed circuit board (PCB)

The present invention relates to a hard disk drive device and a method for determining contact points between a head and a disk, and more particularly to a method for determining contact points between disks in a head having a heater coil.

Hard disk drives have a plurality of magnetic heads that are coupled to a rotating disk. The head writes and reads information by magnetizing and sensing magnetic fields on the disk surface. Each head is attached to a flex arm that forms a sub-component of the head gimbal assembly. The head gimbal assembly (HGA) is supported from the actuator arm. The actuator arm has a voice coil motor (VCM) that can move the head across the surface of the disk.

The disk is rotated by the spindle motor of the hard disk drive. Rotation of the disk generates air flow in the hard disk drive. Each head has an air bearing surface that cooperates with the air flow to create an air bearing between the head and the adjacent disk surface. Air bearings eliminate or minimize the mechanical wear between the head and the disk. The height of the air bearing is generally regarded as the flying height of the head.

The magnetic field is detected by having the head inversely proportional to the flying height of the head. As such, the strength of the magnetic field on the disc is also inversely proportional to the flying height. Larger flight heights result in smaller magnetic fields on the disk.

For various reasons, the head's flight height will change during the operating period of the disk drive. This change in flight height results in degradation of data recording on the disc. For example, weakly recorded data can cause errors during read operations. Therefore, it is desirable to accurately determine and adjust the flying height of the head in the hard disk drive device.

Advanced types of heads have been produced, including heater coils. Current is provided to a heater coil to generate heat, and physically extends the head to move the write and read elements closer to the disk. These types of heads are also called fly on demand heads. The flight height of the FOD head can be varied by varying the amount of power provided to the heater coil.

It is important to create a flying height with a value close to zero. In order to reach the minimum flight height, it is important to know the point of contact between the head and the disc. Attempts to determine head contact include monitoring a position error signal (PES-position error signal) of a servo routine in the disk drive.

1 shows monitoring in the prior art used to determine the head contact point and is a graph showing the position error signal PES value according to the voltage V. FIG.

The result of the foregoing attempt is shown in FIG. 1.

Such curves have a myriad of maximum and minimum peaks. As a result, determining the point at which the head contacts the disk is a difficult problem.

An object of the present invention is to provide a hard disk drive device capable of accurately determining the contact point of the head and the disk.

Another object of the present invention is to provide a method for determining a contact point of a head and a disk in a hard disk drive.

According to another aspect of the present invention, a hard disk device includes a disk, a head coupled to a disk, a write element, a read element, and a heater coil, a voice coil motor coupled to the head, And a controller coupled with the head and the voice coil motor.

The controller supplies power to the heater coil, performs a process of collecting the estimated error data, and determines a deviation value of the estimated error data to determine a contact point of the head and the disk.

According to another aspect of the present invention, there is provided a method of determining a contact point between a head and a disk of a hard disk drive, the method comprising: supplying power to a heater coil of a head, and collecting estimated error data; Performing a process, and determining a deviation value of the estimated error data to determine a point of contact between the head and the disc.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

A hard disk drive (HDD) according to the present invention includes a fly on demand (FOD) head and includes a process for determining contact between the fly on demand (FOD) head and the disk. The head includes a heating coil capable of receiving various levels of power. The process may include a process for determining head position estimate error data. Variable values in the estimated error data are generated by inputting different power values and used to determine the point of contact between the head and the disk. The process also collects values of a plurality of signal amplification gain control signals and calculates an average of the values of the plurality of signal amplification gain control (SAGC) signals. The average of signal amplification gain adjustment (SAGC) signal values at different power levels can be generated and used to determine the point of contact between the head and the disk.

2 is a view showing a hard disk drive device according to the present invention.

Referring to FIG. 2, the hard disk drive 10 device may include one or more magnetic disks 12 that are rotated by a spindle motor 14. The spindle motor 14 may be mounted on a base plate 16. The hard disk drive 10 may further include a cover 18 surrounding the disk 12.

The hard disk drive 10 includes a plurality of heads 20 located adjacent to the disk 12.

3 is an enlarged view of a head of the hard disk drive of FIG. 2.

As shown in FIG. 3, the head 20 may be divided into a write element 22 and a read element 24. The write element 22 magnetizes the disc to write data. The read element 24 senses a magnetic field formed in the disc 12 to read data. The read device 24 is made of a magneto-resistive material, which is a material having a resistance that changes linearly with a change in magnetic flux.

The head 20 also includes a heater coil 25. Current may be supplied to the heater coil 25 to generate heat within the head 20. This heat physically expands the head 20 and moves the write element 22 and read element 24 closer to the disk 12.

Referring to FIG. 2, each head 20 is mounted in equilibrium with a flex arm 26 belonging to a portion of the head gimbal assembly (HSA). The curved arm 26 is attached to an actuator arm 28 which is mounted centrally on a base plate 16 by a bearing assembly 30. A voice coil 32 is attached to the actuator arm 28. The voice coil 32 is coupled with a magnet assembly 34 to produce a voice coil motor 36. Providing current to the voice coil 32 creates a torque that vibrates the actuator arm 28 and causes the head 20 to move close to the disk 12.

The hard disk drive 10 device includes a printed circuit board assembly comprising a plurality of integrated circuits 40 coupled with a printed circuit board 42. assembly 38) may be further provided. The PCB 40 is connected to the voice coil 32, the head 20, and the spindle motor 14 by wires (not shown).

4 is a schematic diagram illustrating an electrical circuit in the hard disk drive of FIG. 2.

Referring to FIG. 4, an electrical circuit 50 for writing and reading data on the disk 12 is shown. The electrical circuit 50 includes a pre-amplifier circuit 52 coupled to the head 20. The preamplifier circuit 52 has a read data channel 54 and a write data channel 56 connected to the read and write channel circuit 58. The preamplifier 52 also has a read / write enable gate 60 connected to the controller 64. By activating the read and writable gate 60, data can be written to or read from the disk 12.

Read and write channel circuitry 58 is connected to controller 64 through each of write and read channels 66 and 68. The controller 64 is connected to the controller 64 through each of the read gate RG 70 and the write gate WG 72.

The read gate 70 is activated when data is read from the disk 12. The write gate 72 is activated when data is written to the disk 12. The controller 64 may be a digital signal processing device operated according to a software routine. The software routine includes procedures for writing or reading data from the disk 12. The read and write channel circuit 58 and the controller 64 are also connected with a motor control circuit 74 that controls the voice coil motor 36 and the spindle motor 14 of the hard disk drive 10. do.

The controller 64 may be connected to a non-volatile memory device 76. For example, the memory device 76 may be a read only memory. The memory device 76 may include instructions for operating the controller 64 and the disk drive 10. Alternatively, the controller 64 may have embedded firmware for operating the hard disk drive.

The controller 64 may be connected by the heater coil 25 and the preamplifier 52 and the conductive wires 78 of each head. The controller 64 may supply a current to the heater coil 25 to control the flying height of the head.

FIG. 5 is a diagram schematically illustrating a read channel in the electrical circuit of FIG. 4.

Referring to FIG. 5, functional blocks of a read channel and a preamplifier of a hard disk drive are shown. The read channel includes an amplifier 80 coupled with the head (not shown). The amplifier 80 adjusts the amplitude of the signal read by the head. The amplified signal is filtered by a filter 82 and converted into a digital bit string by an analog-to-digital converter 84.

The gain of the amplifier 80 is adjusted by the automatic gain control circuit 86. The automatic gain control circuit 86 receives the output of the digital to analog converter 84 as an input and supplies an analog control signal to the amplifier 80. The analog control signal is generally referred to as a SAGC-Servo Amplifier Gain Control.

The control signal is inversely proportional to the amplitude of the read signal. A weak signal results in a large value control signal. The large value control signal increases the gain of the automatic gain adjustment circuit 86 and raises the amplitude of the read signal. The signal read by the head is inversely proportional to the head's flying height. As a result, the control signal is proportional to the flight height. Large control signals indicate an increase in flight height.

FIG. 6 is a diagram schematically illustrating a servo loop of the hard disk drive of FIG. 2.

With reference to FIG. 6, the functional block of the servo routine used to control the position of the head can be seen schematically. The routine includes a junction 100 that sums the target value of the head position and the output value of the estimator 102. The output of the junction 100 becomes a position error signal PES provided to the servo controller 104. The servo controller 104 provides a drive signal u (k) to the plant 106. Here, the plant 106 includes a voice coil motor, an actuator arm and the like. Another junction 108 sums the measured position of the head with the estimated position provided by the estimator 102. The output of the junction 108 becomes a measurer error value.

7 is a flowchart illustrating a process in accordance with the present invention for performing calculations to collect data and obtain data that can be used to determine contact between the head and the disk.

Data for determining contact between the head and the disk can be obtained using the process of FIG. The head moves to the first track position on the disc (step 200).

Power is provided to the heater coil of the head (202).

A plurality of servo amplification gain control signal (SAGC) values are collected and obtained while the disk is rotating several times, and the average of the SAGC values is calculated (step 204).

A plurality of meter error values (EstErr) are collected and obtained during the rotation of the disk several times, and the deviation of the meter error value (EstErr) is obtained. The meter error value can be obtained according to Equation 1 below.

[Equation 1]

here,

Vrss = voltage applied to the heater coil

N = number of meter error values collected

EstErr (i) = the i-th collected instrument error value.

The power supplied to the heater coil is cut off (step 208).

The delta SAGC value of the servo amplification gain control signal SAGC is the average of the servo amplification gain control signal SAGC at the current power level and the average at the last power level. The difference is the value of the servo amplification gain control signal (average SAGC). As such, the EST difference EST delta is calculated as the difference value of the error measurement variations between the most recent power levels (step 212).

The delta SAGC value of the floating servo amplification gain control signal SAGC is calculated as a moving average of the SAGC delta values at n previous power levels (step 214). The moving EST delta is calculated as the moving average of the EST delta values at n previous power levels (step 216).

The spanSAGCdelta value of the SAGC delta value is calculated as the last n ranges of SAGC delta values (step 218). The spanESTdelta value is calculated as the last n ranges of the entire width of the EST delta value (step 220).

The SAGC limitSAGC may be calculated as a sum of 1.5 times the total SAGC delta (moving SAGC delta) value and the spanESTdelta of the EST delta value (step 224).

It is determined whether the SAGC delta value has a larger value than the SAGC limitSAGC or whether the EST delta value has a larger value than the EST limitEST (step 226). If not, it indicates that the power supply level is increasing, and then the process returns to step 204 described above (step 228). If the determination result in step 226 is large, the power level is stored (step 230).

Determine whether the head is on the last track (step 232). If the head is not on the last track, the head moves to the next track and moves to step 202 to continue the process of FIG. 7 (step 234). If the head is on the last track, the average value of SAGC is replaced with the previous value (step 236). Second order curve fit may be performed on the data. The process shown in FIG. 7 is performed by the controller 64 according to data and operations stored in the memory. Data and operations may be organized according to routines performed by the controller 64 and / or external processor.

8 is a graph showing a change value of the power level supplied to the heating coil of the head versus the head position measurement error.

Referring to Figure 8, the difference in the change value in the heating coil voltage difference is shown. The data change is a steep change at the point where the head makes contact with the disk.

9 is a graph showing the power level supplied to the heating coil of the head versus the average SAGC value.

9 shows the average SAGC value versus the coil voltage. This data also indicates that there is a sharp change in the contact where the head makes contact with the disk. The graphs are distinct from the prior art with the numerous transition points shown in FIG. Thus, the prior art has made it difficult to accurately determine the point of contact (of the head and the disk).

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, these terms are only used for the purpose of describing the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the method of determining the contact point between the head and the disk of the hard disk drive device and the hard disk drive according to the present invention has the advantage of easily and accurately determining the connection point between the head and the disk.

Claims (28)

disk; A head coupled with the disk and having a writing element, a reading element, and a heater coil; A voice coil motor coupled to the head; And And a controller coupled to the head and the voice coil motor, The controller Supplying power to the heater coil, Collecting estimated error data corresponding to a difference between the measured position and the estimated position of the head, And determine a deviation value of the estimated error data to determine a point of contact between the head and the disk. The method of claim 1, wherein the estimated error data is A hard disk drive comprising both an estimated head position and a measured head position. The method of claim 1, wherein the controller And determine a deviation value of the estimated error data associated with the plurality of power levels supplied to the heater coil. The method of claim 3, wherein the controller And determining a delta between the deviation value at the first power level and the deviation value at the second power level. The method of claim 3, wherein the deviation value and the power level is A hard disk drive characterized in that it is plotted. The method of claim 1, wherein the deviation value

Hard disk drive, characterized in that calculated according to the equation. (Where, Vrss = voltage applied to the heater coil, N = number of estimated error data collected, EstErr (i) = i-th estimated error data collected) disk; A head coupled with the disk and having a writing element, a reading element, and a heater coil; A voice coil motor coupled to the head; And Supplying power to the heater coil Collecting estimated error data corresponding to a difference between the measured position and the estimated position of the head, And a circuit arrangement for determining a deviation value of the estimated error data to determine a point of contact between the head and the disk. Claim 8 was abandoned when the registration fee was paid. The method of claim 7, wherein the estimated error data is A hard disk drive comprising both an estimated head position and a measured head position. Claim 9 was abandoned upon payment of a set-up fee. The apparatus of claim 7, wherein the circuit device is And determine a deviation value in the estimated error data associated with the plurality of power levels supplied to the heater coils. Claim 10 was abandoned upon payment of a setup registration fee. The apparatus of claim 9, wherein the circuit device is And determining a delta between the deviation value at the first power level and the deviation value at the second power level. Claim 11 was abandoned upon payment of a setup registration fee. The method of claim 9, wherein the deviation value and the power level is A hard disk drive characterized in that it is plotted. Claim 12 was abandoned upon payment of a registration fee. 8. The method of claim 7, wherein the deviation value is

Hard disk drive, characterized in that calculated by the equation. (Where, Vrss = voltage applied to the heater coil, N = number of estimated error data collected, EstErr (i) = i-th estimated error data collected) A program storage medium storing a program for a hard disk drive including a disk and a head having a write element, a read element, and a heater coil, the program storage medium comprising: The storage medium is Allow a controller to power a heater coil, collect estimated error data corresponding to the difference between the measured position and the estimated position of the head, and determine the point of contact between the head and the disk. And a program for determining a deviation value of the estimated error data. The method of claim 13, wherein the deviation value is A program storage medium comprising both estimated head positions and measured head positions. The method of claim 13, wherein the program is And causing the controller to determine estimated error data associated with a plurality of power levels supplied to a heater coil. The method of claim 15, wherein the program is And cause the controller to determine a difference between the deviation value at the first power level and the deviation value at the second power level. The method of claim 15, wherein the program is And causing the deviation values and the power levels to be plotted. The method of claim 13, wherein the deviation value is

The program storage medium, characterized in that calculated according to the equation. (Where, Vrss = voltage applied to the heater coil, N = number of estimated error data collected, EstErr (i) = i-th estimated error data collected) In the method of determining the contact point between the head of the hard disk drive and the disk, Supplying power to the heater coil of the head; And Collecting estimated error data corresponding to the difference between the measured position and the estimated position of the head, and determining a deviation value of the estimated error data to determine a point of contact between the head and the disc. And a contact point between the head and the disk. Claim 20 was abandoned upon payment of a registration fee. 20. The method of claim 19, wherein the estimated error data is A method for determining a point of contact between a disc and a head comprising both an estimated head position and a measured head position. Claim 21 was abandoned upon payment of a registration fee. The method of claim 19, wherein the determining method is And determining a deviation value in the estimated error data associated with the plurality of power levels supplied to the heater coils. Claim 22 was abandoned upon payment of a registration fee. The method of claim 21, wherein the determining method is Determining a small difference (delta) between a deviation value at the first power level and a deviation value at the second power level. Claim 23 was abandoned upon payment of a set-up fee. The method of claim 21, wherein the deviation value and the power level is Further comprising the step of being plotted. Claim 24 was abandoned when the setup registration fee was paid. The method of claim 19, wherein the deviation value is

The contact point determination method between the head and the disk, characterized in that obtained by the equation. (Where, Vrss = voltage applied to the heater coil, N = number of estimated error data collected, EstErr (i) = i-th estimated error data collected) disk; A head coupled with the disk and having a writing element, a reading element, and a heater coil; An amplifier coupled to the head; An automatic gain control circuit coupled with the amplifier for generating a servo amplification gain control (SAGC) signal; A voice coil motor coupled to the head; And And a controller coupled to the head and the voice coil motor, The controller And powering the heater coil, collecting a plurality of SAGC values, and determining an average of the SAGC values to determine a contact point of the head and the disk. The method of claim 25, wherein the controller And determining an average of SAGC values associated with a plurality of power levels supplied to the heater coil. 27. The system of claim 26, wherein the controller is And determine a delta between the average of the SAGC values at the first power level and the average of the SAGC values at the second power level. 27. The method of claim 26, wherein the average of the SAGC values and the power level are A hard disk drive characterized in that it is plotted.

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